Machines such as, for example, compactors, pavers, dozers, loaders, excavators, motor graders, and other types of heavy machinery have different loads to be driven, which may be called as primary load and secondary load. It is known to use an engine to drive the primary load and a pump and motor system to provide the power for the secondary load. The pump and motor system may receive an output from the engine and transfer the power to the secondary load.
When the primary load driven by the engine changes, the output from the engine may change accordingly. As a result, such change may also cause the pump and motor system to change. In this situation, it may be desirable to compensate for the change in the pump and motor system to maintain a constant power output.
U.S. Pat. No. 4,490,619 issued to McMinn (“619 patent”), discloses a hydraulic driven electric generator and air conditioning system for simultaneously generating controlled quality electrical power and producing air conditioning in a desired area. The system includes a variable displacement hydraulic pump driven by a prime engine for driving the generator. The generator includes a speed pickup sensor for sensing the speed of the generator and responsively controlling the variable displacement pump to maintain a constant generator speed.
The '619 patent may compensate for the changes in generator speed, but it does not sense a change in engine speed based on a change in a primary load, change the engine speed to compensate for the primary load change, and then change a displacement of a pump to maintain a constant secondary load. Thus, the '619 patent does not maintain both a primary load and a secondary load in desired manners.
The present disclosure is directed at overcoming one or more of the problems or disadvantages in the prior art control systems.